La croissance de polymères bidimensionnels a été étudiée sous ultra-haut vide sur des surfaces métalliques par microscopie à effet tunnel (STM). La première étude concerne la croissance de réseaux nanoporeux covalents bidimensionnels obtenus par réaction de déshydratation des molécules d'acide 1.4 diboronique (BDBA). Les meilleurs réseaux sont obtenus pour les dépôts à flux élevés sur des substrats d'Argent chauffés à 150°C. La deuxième étude concerne la réaction chimique entre les molécules de 1,2,4,5 tétracyanobenzène (TCNB) et les atomes de Fer. La formation de liaison covalente entre les molécules et les atomes de Fer est thermiquement activée par des recuits à 200°C et permet la formation d'octacyanophtalocyanine de Fer. Ce travail ouvre de nouvelles perspectives pour la fabrication de matériaux 2D originaux obtenus par des réactions chimiques de surface. / The growth of two dimensional polymers has been studied under ultra-high vacuum on metallic surfaces by scanning tunnelling microscopy (STM). The first study relates on the growth of two dimensional covalent nanoporous networks obtained after dehydratation reaction of the 1,4 diboronic acid benzene molecule (BDBA). The best networks have been obtained with high molecular flux on silver metallic substrates maintained at 150°C during deposition. The second study relates on chemical reaction between the 1, 2, 4, 5 tetracyanobenzene molecule (TCNB) and iron atoms. The reaction takes place after an annealing at 200°C. In that case some iron octacyanophthalocyanine have been successfully synthesised at surfaces. This work opens new perspectives for the fabrication of 2D original materials by chemical reactions on surfaces.

Dans ce rapport de thèse, nous présentons les résultats obtenus avec la croissance d'assemblages supramoléculaires hautement cristallins et stables à température ambiante sur des surfaces isolantes d'halogénures d'alcalins. L'objectif de cette étude est de caractériser structurellement ces réseaux auto-assemblés et de mettre en évidence l'ensemble des forces d'interaction mises en œuvre dans les processus de croissance et de diffusion, en combinant la microscopie à force atomique en mode non contact (nc-AFM) sous ultravide et des calculs théoriques basés sur la théorie de la fonctionnelle de la densité (DFT) et la dynamique moléculaire. Nous montrons comment des paramètres bien définis concernant le choix de la molécule d'une part tels que sa taille, sa forme, sa symétrie, sa flexibilité et sa fonctionnalité, et le choix du substrat d'autre part, influent sur la morphologie de croissance et permettent de contrôler les propriétés de diffusion des molécules en surface et donc la structure supramoléculaire résultante. / In this thesis, we report the results obtained with the growth of highly crystalline and stable supramolecular assemblies at room temperature on insulating surfaces of bulk alkali halides single crystals. The objective of this study is to structurally characterize these self-assembled networks and understand all the interaction forces involved in the growth and diffusion processes. This is performed by joint non-contact atomic force microscopy (nc-AFM) experiments in ultrahigh vacuum and theoretical calculations based on density functional theory (DFT) and molecular dynamics. We show how well-defined parameters for the choice of the molecule on the one hand such as size, shape, symmetry, flexibility and functionality, and the choice of the substrate on the other hand, influence the morphology growth and serve to steer the structure and diffusion properties of such systems.

Designing novel nanostructures which exploit the self-assembly capabilities of biomolecules yields a promising approach to control matter at the nanoscale. Here, the homochiral molecular self-assemblies of the methionine and tyrosine amino acids on the monocrystalline Ag(111) and Cu(111) surfaces are characterized by means of scanning tunneling microscopy (STM) and spectroscopy (STS), helium atom scattering (HAS), x-ray photoelectron spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS) in ultrahigh vacuum (UHV). On Ag(111), methionine self-assembles into supramolecular chains following the <110> substrate axis, forming regular nanogratings with tunable periodicity. Within the nanowires, a zwitterionic dimerization scheme is revealed. STS shows that the biomolecular nanostructures act as tunable one-dimensional quantum resonators for the surface state electrons. Zero-dimensional electronic confinement is achieved by positioning single iron atoms in the molecular trenches. This shows a novel approach to control the dimensionality of surface state electrons. The nanogratings were exploited to steer the spontaneous one-dimensional ordering of cobalt and iron atoms. For T > 15 K, the metal species self-align into homogeneously distributed chains in between the biomolecular trenches with ~25 Å interatomic distace. For Co, the dynamics of the self-alignment was monitored, revealing a reduced mobility in comparison with isolated Co atoms on bare Ag(111). On Cu(111), the self-assembly of methionine is influenced by the substrate reactivity and its temperature during molecular deposition. For T < 273 K, the biomolecules assemble in anisotropic extended clusters oriented with a -10° rotation off the <110> substrate orientations, whereas above 283 K a regularly ordered 1D phase arises with a +10° rotation off these high-symmetry axis. XPS reveals a structural transformation triggered by a thermally activated deprotonation of the zwitterionic ammonium group. On Ag(111), tyrosine self-assembles above a critical temperature into linear structures primarily following the substrate crystalline symmetry. A zwitterionic non-covalent molecular dimerization is demonstrated, NEXAFS data providing evidence of a non-flat adsorption of the phenyl ring. This recalls the geometrical pattern of methionine on Ag(111) and supports a universal self-assembling scheme for amino acids on close-packed noble metal surfaces, the different mesoscopic ordering being determined by the side chain reactivity.

Designing novel nanostructures which exploit the self-assembly capabilities of biomolecules yields a promising approach to control matter at the nanoscale. Here, the homochiral molecular self-assemblies of the methionine and tyrosine amino acids on the monocrystalline Ag(111) and Cu(111) surfaces are characterized by means of scanning tunneling microscopy (STM) and spectroscopy (STS), helium atom scattering (HAS), x-ray photoelectron spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS) in ultrahigh vacuum (UHV). On Ag(111), methionine self-assembles into supramolecular chains following the <110> substrate axis, forming regular nanogratings with tunable periodicity. Within the nanowires, a zwitterionic dimerization scheme is revealed. STS shows that the biomolecular nanostructures act as tunable one-dimensional quantum resonators for the surface state electrons. Zero-dimensional electronic confinement is achieved by positioning single iron atoms in the molecular trenches. This shows a novel approach to control the dimensionality of surface state electrons. The nanogratings were exploited to steer the spontaneous one-dimensional ordering of cobalt and iron atoms. For T > 15 K, the metal species self-align into homogeneously distributed chains in between the biomolecular trenches with ~25 Å interatomic distace. For Co, the dynamics of the self-alignment was monitored, revealing a reduced mobility in comparison with isolated Co atoms on bare Ag(111). On Cu(111), the self-assembly of methionine is influenced by the substrate reactivity and its temperature during molecular deposition. For T < 273 K, the biomolecules assemble in anisotropic extended clusters oriented with a -10° rotation off the <110> substrate orientations, whereas above 283 K a regularly ordered 1D phase arises with a +10° rotation off these high-symmetry axis. XPS reveals a structural transformation triggered by a thermally activated deprotonation of the zwitterionic ammonium group. On Ag(111), tyrosine self-assembles above a critical temperature into linear structures primarily following the substrate crystalline symmetry. A zwitterionic non-covalent molecular dimerization is demonstrated, NEXAFS data providing evidence of a non-flat adsorption of the phenyl ring. This recalls the geometrical pattern of methionine on Ag(111) and supports a universal self-assembling scheme for amino acids on close-packed noble metal surfaces, the different mesoscopic ordering being determined by the side chain reactivity.

Designing novel nanostructures which exploit the self-assembly capabilities of biomolecules yields a promising approach to control matter at the nanoscale. Here, the homochiral molecular self-assemblies of the methionine and tyrosine amino acids on the monocrystalline Ag(111) and Cu(111) surfaces are characterized by means of scanning tunneling microscopy (STM) and spectroscopy (STS), helium atom scattering (HAS), x-ray photoelectron spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS) in ultrahigh vacuum (UHV). On Ag(111), methionine self-assembles into supramolecular chains following the <110> substrate axis, forming regular nanogratings with tunable periodicity. Within the nanowires, a zwitterionic dimerization scheme is revealed. STS shows that the biomolecular nanostructures act as tunable one-dimensional quantum resonators for the surface state electrons. Zero-dimensional electronic confinement is achieved by positioning single iron atoms in the molecular trenches. This shows a novel approach to control the dimensionality of surface state electrons. The nanogratings were exploited to steer the spontaneous one-dimensional ordering of cobalt and iron atoms. For T > 15 K, the metal species self-align into homogeneously distributed chains in between the biomolecular trenches with ~25 Å interatomic distace. For Co, the dynamics of the self-alignment was monitored, revealing a reduced mobility in comparison with isolated Co atoms on bare Ag(111). On Cu(111), the self-assembly of methionine is influenced by the substrate reactivity and its temperature during molecular deposition. For T < 273 K, the biomolecules assemble in anisotropic extended clusters oriented with a -10° rotation off the <110> substrate orientations, whereas above 283 K a regularly ordered 1D phase arises with a +10° rotation off these high-symmetry axis. XPS reveals a structural transformation triggered by a thermally activated deprotonation of the zwitterionic ammonium group. On Ag(111), tyrosine self-assembles above a critical temperature into linear structures primarily following the substrate crystalline symmetry. A zwitterionic non-covalent molecular dimerization is demonstrated, NEXAFS data providing evidence of a non-flat adsorption of the phenyl ring. This recalls the geometrical pattern of methionine on Ag(111) and supports a universal self-assembling scheme for amino acids on close-packed noble metal surfaces, the different mesoscopic ordering being determined by the side chain reactivity. / Science, Faculty of / Chemistry, Department of / Graduate

No description available.

The ability of RNA bases to self-assemble into larger structures is an important research area relevant to the origins of life. In the RNA helix the bases are arranged on a sugar-phosphate carcass but it has been suggested that the initial ordering could form on a flat surface. This thesis is an attempt to establish experimentally whether the complementary RNA bases, adenine and uracil, have the ability to self-assemble into large ordered structures when adsorbed on metal and mineral surfaces. The Au (111) surface was chosen as a preferred substrate as it is flat, relatively free of defects, chemically inert and reconstructs in a characteristic pattern of corrugation lines, which provide a reference for crystallographic directions. Six of the molecular phases shown were observed for the first time with molecular resolution and the possible two-dimensional arrangements of adenine and uracil molecules for these phases are proposed. The pure adenine and pure uracil structures have chiral unit cells and in the case of pure uracil alternating monochiral domains within the polychiral islands are created. Well-ordered intricate uracil-adenine bimolecular networks were also observed. The self-assembly of both uracil and adenine appears to be weakly influenced by the surface crystallography. The (100) surface of the mineral pyrite (FeS₂) was chosen as the alternative substrate as it is the most common face that occurs naturally in pyrite crystals. The experiments show the formation of small adenine and uracil crystals at the terrace edges. Neither uracil nor adenine were observed to form a monolayer on the surface of the terraces. The results of the experiments described in this thesis are very interesting in terms of establishing the possible mechanisms for creating regular chiral molecular networks and provide a useful insight into the role of surfaces in the processes of self-assembly of RNA bases.

This thesis describes investigations into the role of non-stoichiometry in the surface and bulk properties of SrTiO₃ single crystals. A family of (n×n) reconstructions, where n = 2, 3, 4, 5, 6 are produced by argon ion sputtering of the SrTiO₃ (111) single crystals and subsequent annealing in UHV or in an oxygen rich environment. The sputtering process introduces defects or oxygen vacancies in the surface region of the sample, whilst the annealing gives rise to surface reconstructions. The surface preparation conditions such as sputtering time, annealing temperature and environment are optimized to obtain various reconstructions in a controlled and reproducible manner. High resolution STM images of these reconstructions are also obtained and utilized in the investigation of the surface reactivity. Fullerene molecules are deposited on the reconstructed surfaces to elucidate the surface reactivity through template assisted growth. Fullerene molecules are first deposited with substrate surfaces held at room temperature. Being the most highly reduced among the (n×n) family, the 5×5 reconstruction significantly influenced the growth of fullerenes. Both C₆₀ and C₇₀ adsorb as individual molecules and produce clusters with magic numbers. The 4×4 and 6×6 reconstructed surfaces encourage the formation of close-packed structures upon the deposition at room temperature. When the surface covered with fullerenes is heated to a temperature of around 200 °C, epitaxial islands are observed. The 6×6 reconstructed surface appeared to be less reactive than the 4×4. Electrical transport, cathodoluminescence (CL) and electron spin resonance (ESR) experiments are also carried out to investigate the effect of oxygen vacancies on the bulk properties of UHV annealed SrTiO₃ single crystals. Thermal reduction leads to carrier doping of the material, which not only gives rise to electrical conduction but also induces room temperature luminescence. Both the electrical conductivity and CL intensity increases with annealing time. The work presented in this thesis provides insight into the defect driven properties in both the surface and bulk of SrTiO₃ single crystals, which could play an important role in the development of oxide-based electronic devices.

Cette thèse vise principalement à décorer des phtalocyanines avec des groupes de reconnaissance supramoléculaires pour induire leur auto-assemblage pour la première fois avec ces chromophores robustes imitant les bactériochlorophylles chlorosomales naturelles. D’autre part, cette thèse est également dédiée à la méthodologie de synthèse des complexes à trois étages avec des lanthanides complexant des porphyrines et phtalocyanines encombrantes.La première partie présente quelques concepts de base et des exemples segéstifs dans la biomimétique et l’auto-assemblage moléculaire. Les auto-assemblages biomimétiques des bactériochlorophylle c, d, e ont été examinés suivie par la synthèse, la séparation des régioisomères des phtalocyanines et des cellules solaires construites avec des phtalocyanines. La deuxième partie présente des travaux originaux sur une série d'antennes pour la coolléction de la lumière, comme les acylphthalocyanines qui font d'auto-assemblage avec des groupes carbonyle comme motifs de reconnaissance, un atome de zinc central et diverses chaînes alkyle de solubilisation. Ces nouveaux composés pourraient s’auto-assembler de la même manière que les bactériochlorophylles naturelles. La troisième partie de cette thèse se concentre sur les propriétés électrochimiques et magnétiques de lanthanides-porphyrine-phtalocyanine complexes sandwich ‘’triple deckers’’ volumineux, synthétisés par une nouvelle méthode sous irradiation avec des micro-ondes. Le site initial de l'oxydation ou de réduction de ce type de molécules à trois étages a d'abord été attribué par la combinaison de la spectroélectrochimie de couche mince. / This thesis mainly aims to decorate phthalocyanines with supramolecular recognition groups for inducing their self-assembly for the first time with these robust chromophores mimicking the natural chlorosomal bacteriochlorophylls. Meanwhile, this thesis is also dedicated to the synthetic methodology of bulky lanthanide porphyrin phthalocyanine triple-decker complexes. The first part provides some basic concepts and some delicate examples in biomimetics and molecular self-assembly, then biomimetic bacteriochlorophyll c, d, e self-assembles were simply reviewed, followed by the introduction on the synthesis, regioisomer separation of phthalocyanines and phthalocyanine-sensitized solar cells. The second part presents a series of light-harvesting antennas, namely self-assembling acyphthalocyanines, with carbonyl groups as recognition motifs, a central zinc atom and various solubilizing alkyl chains, which could self-assemble in the same way as the natural bacteriochlorophylls. These assemblies were characterized by UV-Vis, Variable-temperature UV-Vis and 1H-NMR spectra. The third part of this thesis focuses on the electrochemical and magnetic properties of bulky lanthanide porphyrin phthalocyanine triple-decker complexes synthesized by microwave-mediated, therein, the initial site of oxidation/reduction on this type of triple-decker molecules was firstly assigned by combining the thin-layer spectroelectrochemistry and the assignments of the electronic absorption spectra. Furthermore, the different single-molecule magnet behaviors of the corresponding Tb and Dy triple-decker complexes were also studied.

No description available.